Hitherto, in an automatic inserting apparatus of this type, in order to improve the production of printed circuit boards with electronic parts actually mounted thereon, it is necessary to quickly insert lead wires of the electronic parts into inserting holes in the printed circuit board without error.
In the conventional apparatus, a guide mechanism for guiding the lead wires of the electronic parts towards the inserting holes in the printed circuit board is so arranged as to contact the printed circuit board directly to enable the insertion of the electronic parts retained by a retaining mechanism. While the lead wires of the electronic parts can be assuredly inserted into the inserting holes in the printed circuit board by the above described guide mechanism, the guide mechanism has to contact the printed circuit board directly, and there is a problem in that the interval between the electronic parts to be inserted must be rendered great, making it difficult to achieve a high density actual mounting of the electronic parts on the printed circuit board.
In view of the above, in order to improve the actual mounting density of the electronic parts on the printed circuit board, there has been proposed an apparatus wherein guide pins are provided so as to extend through the inserting holes in the printed circuit board in a direction counter to the direction of insertion of the electronic parts whereby the lead wires of the electronic parts can be guided by the guide pins so as to be introduced into the inserting holes in the printed circuit board. In the apparatus of the above described construction, since a mechanism for introducing the lead wires of the electronic parts into the inserting holes in the printed circuit board does not directly contact the surface of the printed circuit board, the actual mounting density of the electronic parts on the printed circuit board can be improved. Hereinafter, the conventional automatic mounting apparatus for the electronic parts utilizing this mechanism will be described.
As shown in FIG. 1, a taping component 1 of radial type is such that two lead wires 5 of electronic parts 4 which extend in the same direction are retained in equally spaced relationship by a cardboard tape 2 and an adhesive tape 3. It is to be noted that, in the drawings, 6 represents feed holes formed by punching the cardboard tape 2 and the adhesive tape 3, and the taping component 1 can be transported at any time by driving a feed mechanism while projecting parts (not shown) of the feed mechanism of the inserting apparatus are engaged in the feed holes 6. The taping component 1 so fed is such that, as shown in FIG. 2, the lead wires 5 can be cut by a plain cutter 8 adapted to be slid in a direction shown by the arrow A by an external drive such as an air cylinder and having an L-shaped projection 7 at the free end thereof, and a lead cutter 9 arranged so as to extend in a horizontal direction and slidable in a direction shown by B. In addition, by the plain cutter 8 and a tape cutter 10 arranged so as to extend vertically and slidable in a direction shown by C, the cardboard tape 2 and the adhesive tape (not shown) of the taping electronic component 1 is cut. Within the above described plain cutter 8, a cylinder 11, a piston 12, and a spring 13 are incorporated, and when air is supplied from an air inlet 14 in the plain cutter 8, the piston 12 is slid so as to compress the spring 13 and to permit a rod 15, provided integrally with the piston 12, to project outwards from a cutting plane of the plain cutter 8 thereby to retain the cardboard tape 2, but when the air supply is interrupted, the piston 12 is slid in the reverse direction by a compressive force of the spring 13 to retract the rod 15 inwards from the cutting plane of the plain cutter 8. In this construction, the lead wires 5 and both the cardboard tape 2 and the adhesive tape 3 of the taping component 1 which is intermittently fed to this cutting zone are simultaneously cut. FIGS. 3(a) to 3(c) show examples of the electronic parts 4 after cutting.
The electronic parts 4 wherein the lead wires 5 have been cut in a predetermined length are, as shown in FIGS. 4 and 5, retained by an inserting chuck 16 with the tips of the lead wires 5 inserted into guide holes 18 in guide plates 17. The guide plates 17 are of a paired construction and they can be, as shown in FIGS. 5 and 6, united together and separated from each other as the necessity arises. In the condition wherein the guide plates 17 are united together, the guide holes 18, constricted at the center, but enlarged at the opposite ends, can be formed. Since the opposite ends of the guide holes 18 are thus enlarged while the center thereof is constricted, the position of the lead wires 5 can be readily inserted into the guide holes even if displaced to a certain extent. Below the guide plates 17, a printed circuit board 20 supported by a printed circuit board guide 19 is positioned, and inserting holes 21 in the printed circuit board 20 are inserted from below with guide pins 23 provided on a guide block 22. The tips of the guide pins 23 are inserted from below into the guide holes 18 in the guide plates 17 with the lead wires 5 and the guide pins 23 contacting together at the center of the guide holes 18 in the guide plates 17 as shown in FIG. 7. The tips of the guide pins 23 are provided with recesses 24 equal to or greater than the diameter of the lead wires 5, and the tips of the lead wires 5 are inserted in the recesses 24. When the lead wires 5 are inserted in the recesses 24, the guide plates 17 which separate to divide the guide holes 18 as shown in FIG. 6 are released, and the electronic part 4 is pushed downwards by a pusher rod 25 while the inserting chuck 16 separates from the electronic part 4. Because of this, the electronic part 4 is advanced downwards while sandwiched between the guide pins 23 and the pusher rod 25, with the lead wires 5 consequently inserted into the inserting holes 21 in the printed circuit board 20, thereby completing the inserting operation.
However, where such a method for inserting the taping component is adopted, since the tips of the guide pins 23 must necessarily be provided with the recesses 24 for receiving the tips of the lead wires 5 for avoiding the separation of the lead wires 5 from the guide pins 23, and accordingly, since the outer diameter of the guide pins 23 must necessarily be greater than the outer diameter or the lead wires 5, the inserting holes 21 in the printed circuit board 20 through which the guide pins 23 are to be inserted will be of a greater size than the outer diameter of the lead wire 5 and, when the lead wires 5 are inserted into the inserting holes 21, there is a problem in that a great gap is created and a soldering defect tends to occur. In addition, since the inserting holes 21 are of increased size, it is necessary to enlarge an electroconductive pattern therearound and, as a result thereof, there is a problem in that the actual mounting density of the printed circuit board 20 is reduced.
Moreover, while it is a recent trend to automatically insert the electronic part 4 having three lead wires 5 such as a transistor shown in FIGS. 8 and 9, the automatic insertion of such an electronic part 4 is so structured as to receive only the opposite two lead wires 5 by means of the guide pins 23 and to insert the intermediate lead wire 5 without any guide and, in this case, even if the intermediate lead wire 5 is positioned by the guide plates 17, it often happens that this intermediate lead wire does not completely align with the inserting hole 21 in the printed circuit board 20 and cannot be inserted because of its abutment against the upper surface of the printed circuit board 20, and because of this, the diameter of the inserting holes 21 in the printed circuit board 20 cannot be reduced.
Furthermore, a mechanism for moving the guide pins 23 up and down in the conventional automatic inserting apparatus for the electronic parts is of a construction as shown in FIG. 10, wherein the guide pins 23 are fixed on the tip of the guide block 22 and a lever stopper 26 is fixed to the guide block 22. The guide block 22 is normally upwardly biased through an elevating rod 29 by means of a spring 27 and a spring seat 28. Therefore, it is so constructed that, when a lever 30 is elevated, the elevating rod 29 lifts the guide block 22 with the guide pins 23 inserted through the inserting holes 21 in the printed circuit board 20.
However, when the guide pins 23 extend through the inserting holes 21 in the printed circuit board 20, the guide pins 23 often contact the inner faces of the inserting holes 21 and, in the event of the failure to extend through the inserting holes 21 as shown in FIG. 11, powdery scraps formed by grinding the printed circuit board 20 and scraps of the lead wire 5 will enter the recesses 24 at the tips of the guide pins 23. Because of this, the recesses 24 are often filled up and the percentage of insertion failure is increased.